ANTIRRHEOSCOPE

n. _ A?n-ti?r-re/o?s-kop. From évripjoia, à flowing back, and oxoneiy, to observe. Fr., antirréoscope. Ger., Antivrheoskop. An instrument devised by J. J. Oppel for observing the manifestations of visual vertigo. It consists of five arallel rollers 2} inches in diameter and 2} feet long, which can all Be rotated in the same direction within a larger cylinder. Fach roller is covered with white paper on which are drawn two black spiral lines, each of 2 turns, Each spiral consists of a wide central black stripe half an inch wide and, half an inch on each side of it, a narrow black stripe. Black and white are thus symmetrically divided. The rollers are all set in motion by turning a disc at the end of the large cylinder, [F.]